--- /dev/null
+# ===========================================================================
+# http://www.gnu.org/software/autoconf-archive/ax_prog_bison.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+# AX_PROG_BISON(ACTION-IF-TRUE,ACTION-IF-FALSE)
+#
+# DESCRIPTION
+#
+# Check whether bison is the parser generator. Run ACTION-IF-TRUE if
+# successful, ACTION-IF-FALSE otherwise
+#
+# LICENSE
+#
+# Copyright (c) 2009 Francesco Salvestrini <salvestrini@users.sourceforge.net>
+# Copyright (c) 2010 Diego Elio Petteno` <flameeyes@gmail.com>
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation; either version 2 of the License, or (at your
+# option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+# Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+# As a special exception, the respective Autoconf Macro's copyright owner
+# gives unlimited permission to copy, distribute and modify the configure
+# scripts that are the output of Autoconf when processing the Macro. You
+# need not follow the terms of the GNU General Public License when using
+# or distributing such scripts, even though portions of the text of the
+# Macro appear in them. The GNU General Public License (GPL) does govern
+# all other use of the material that constitutes the Autoconf Macro.
+#
+# This special exception to the GPL applies to versions of the Autoconf
+# Macro released by the Autoconf Archive. When you make and distribute a
+# modified version of the Autoconf Macro, you may extend this special
+# exception to the GPL to apply to your modified version as well.
+
+#serial 9
+
+# mattst88:
+# Modified YACC assignment to remove -o y.tab.c since we're writing
+# our own .y/.yy rules.
+#
+# Replaced m4_ifnblank(...) with m4_ifval(m4_normalize(...), ...)
+# since m4_ifnblank requires autoconf-2.64.
+
+AC_DEFUN([AX_PROG_BISON], [
+ AC_REQUIRE([AC_PROG_YACC])
+ AC_REQUIRE([AC_PROG_EGREP])
+
+ AC_CACHE_CHECK([if bison is the parser generator],[ax_cv_prog_bison],[
+ AS_IF([$YACC --version 2>/dev/null | $EGREP -q '^bison '],
+ [ax_cv_prog_bison=yes], [ax_cv_prog_bison=no])
+ ])
+ AS_IF([test "$ax_cv_prog_bison" = "yes"], [
+ dnl replace the yacc-compatible compiler with the real bison, as
+ dnl otherwise autoconf limits us to the POSIX yacc.
+ dnl We also change the generated filename to the old one, so that
+ dnl automake's ylwrap can deal with it.
+ YACC="${YACC% -y}"
+ ] m4_ifval(m4_normalize([$1]), [[$1]]),
+ m4_ifval(m4_normalize([$2]), [[$2]])
+ )
+])